Refractory brick is used commonly to line the interior surfaces of vessels within which high temperatures are generated and/or within which an atmosphere corrosive to metals is found. The type of refractory brick employed in such vessels varies with the function of the vessel. For example, refractory brick used for ceramic kilns and furnaces differs from that used in blast furnaces and fluidized-solids reactors. In the last mentioned vessels, refractory brick typically is resistant to both high temperatures and a corrosive or erosive atmosphere resulting from chemical reaction and movement of material within the vessel. A typical example of the latter type vessel is a fluidized-solids chlorination reactor wherein metallic chlorides are produced by treatment of a particulate ore with gaseous chlorine at elevated temperatures.
Conventionally, the refractory lining of a reaction vessel is fabricated from several courses (rows) of refractory brick bonded together with a bonding mortar compatible with the brick. Typically, the mortar is prepared with water. When the refractory lining is dried, most of the water in the mortar is removed. However, a small quantity of water remains in the mortar either as water of hydration, or as chemically uncombined water. In vessels wherein a chlorination reaction is conducted, the presence of such water produces a deleterious effect on the refractory brick and metal shell. For example, in such a chlorination vessel, hot gaseous chlorine will combine with water to form hydrochloric acid. The hydrochloric acid attacks the refractory brick and metal shell causing severe deterioration of these materials, particularly within the inner courses of brick comprising the vessel lining. Such deterioration can cause premature shutdown of the process conducted within the vessel and expensive replacement of the refractory brick lining.
It has been proposed to protect refractory linings by coating the surface of the refractory brick exposed to the interior of the vessel containing the lining with various materials. See, for example, U.S. Pat. No. 1,576,021 (metallic aluminum coating), U.S. Pat. No. 2,336,366 (metallic nickel or nickel alloy), U.S. Pat. No. 2,746,888 (metallic titanium or titanium alloy), U.S. Pat. No. 3,203,785 (viscous aluminasilica mixture), and U.S. Pat. No. 3,330,627 (glazed vitrious silica). Such techniques are expensive and most require special equipment.
It has also been suggested to fabricate refractory linings without utilizing mortar, i.e., laying-up the brick dry. However, this procedure requires machining of the refractory brick to very close tolerances in order to provide a lining which is both structurally sound and impervious to the outside atmosphere and the contents, e.g., gases, solids and liquids, within the vessel. The latter requirement prevents the egress of the contents of the vessel, especially gas charged to or generated within the vessel, to the shell of the vessel and to the atmosphere. Use of the aforesaid dry assembly of refractory brick has not proven to be entirely successful. In chlorination vessels, for example, gaseous chlorine charged to the vessel seeps through the interstices between the refractory brick and is lost to a recovery or waste system. In commercial fluidized bed chlorinators, such loss can be substantial and not only increases chlorine recovery costs but also poses a potential health hazard.